Titanium nitride (TIN) straps are often used in semiconductor devices to provide local interconnections between conductive regions, such as between a polysilicon line and a nearby doped region formed in the semiconductor surface. During the local interconnection formation process conductive filaments or stringers frequently develop along the sidewall oxide regions usually found adjacent the polysilicon lines. Depending on the size and location of these filaments, unwanted shorts between conductors in the semiconductor device may occur which adversely affects device performance.
The current approach to eliminating the problems associated with filaments is to remove any filaments exposed during the dry etching of the TiN, which defines the desired local interconnections, with an additional wet etch, typically using a 10:1:1 solution of H.sub.2 O:NH.sub.4 OH:H.sub.2 O.sub.2. (It is generally believed that the conventional dry etches using carbon tetrachloride and helium do not remove filaments due to sidewall passivation). These wet etches however adversely affect yield. The photoresist exposed to the dry etch process has a tendency to lift during the wet etch. The wet etch then undercuts the photoresist damaging the newly defined TiN local interconnections. Depending on how early in the wet etch the lifting occurs, the damage to the TiN interconnections may range from mild degradation to complete removal of areas of the TiN material.